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Federal Register / Vol. 86, No. 232 / Tuesday, December 7, 2021 / Proposed Rules
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actual stack parameters flowrate or temperature below the modeled stack parameters can result in downwind concentrations higher than those modeled. We note that Rains compliance records, Title V deviation reports, and annual stack tests since August 2, 2018 the effective date of AOC demonstrate a pattern of difficulty complying with the SIP emission limits at all times and difficulty in estimating emissions and flowrates from the pyroscrubber to demonstrate compliance.22 During the 9-week period between when the AOC limits became effective August 2, 2018 and the attainment date October 4, 2018, Rain reported that deviations occurred on 7
separate days for a total duration of 27.2
hours 25.2 hours due to calculated pyroscrubber flowrates less than the AOC requirements, and 2 hours when cold stack emissions exceeded the AOC
emission limits.23 Rain has since identified the need to revise the limits and potentially adjust the methodology used to estimate emissions and flowrates in the pyroscrubber that are contained in the AOC. In March of 2019, Rain conducted the first annual stack test as required by the August 2, 2018
AOC.24 The 2019 stack test report found that the AOC hot stack equation underestimates hot stack emissions during most of the transition from hot stack to cold stack and during no hour did the combined flue gas flow and temperature meet the description of any transition stage. The report then states the AOC limits and conditions do not reflect actual emissions conditions and it is difficult to identify the appropriate transition stage, before recommending that the August 2018 AOCs flue gas flow rates, temperatures, and emissions limits for transitions stages 1, 2, and 3
be replaced with new conditions.
Generally, one stack test may not be determinative, but the EPA believes that it is reasonable to conclude that the problems identified in the 2019 stack test were significant and, in conjunction with the 2018 semiannual monitoring report violations, indicative that the facility not only failed to meet the AOC
requirements during the two days of the stack test, but likely failed to meet the 22 See deviations listed in semiannual monitoring reports for 2018. We also note as dicta that the source continued to experience deviations in 2019
and 2020. The semiannual monitoring reports for 2018, 2019, and 2020 as well as the 2019 and 2020
stack test reports are available in the docket for this action.
23 See deviations listed in semiannual monitoring report for July 1December 31, 2018.
24 Annual stack tests are a requirement of the August 2, 2018 AOC. The 2019 stack test was the first annual stack test performed pursuant to this requirement.

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2018 AOCs transition stage operational requirements during the period between the effective date of the AOC and the attainment date.
The EPA also notes that the semiannual monitoring report for January through June 2020, while not the basis or rational for our decision making, includes additional deviations indicating that the facility continued to have difficulty complying with the limits in the SIP after the attainment date had passed. The report further states that: Rain continues to analyze this and similar deviations to identify a corrective action. The permit requirements do not match actual startup conditions. Rain is in negotiations with EPA and LDEQ to revise the permit requirements to reflect actual start-up conditions.
From the available information, EPA
cannot determine with certainty that the area attained the NAAQS as the emissions and stack parameters at times fall outside the limits and conditions modeled in the approved attainment demonstration. The noted violations of the permit limits or underestimated emissions may have resulted in violations of the one-hour SO2 NAAQS
in areas other than the monitored location. Furthermore, the data demonstrates a clear need for development of a new attainment SIP
with revised limits that better align with the sources operations and modeling to demonstrate attainment.
d. EPAs Proposed Determination Based on our review of the monitor, modeling and compliance data, EPA
proposes to find that the St. Bernard area did not attain the 2010 one-hour SO2 NAAQS by the October 4, 2018
attainment date. The modeling data demonstrates that the emission limits and stack parameters in the AOC
required of the Rain facility were necessary for the St. Bernard area to attain the standard. However, review of Rains compliance record demonstrates that emissions have exceeded those limits, and stack temperatures and flowrates have not met the necessary parameters to demonstrate attainment in the St. Bernard area. As described in the previous section, Rain reported deviations during the period between the effective date of the limits and the attainment date. Rain has also reported underestimation of emissions from the hot stack when comparing estimated emissions to the measured emissions during the 2019 stack test indicative that Rain has failed to meet the AOC
limits since the effective date. We also note, without relying upon, that Rain continued to report deviations in
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additional stack tests and deviation reports from 2018, 2019, and 2020.
Under CAA section 179d2, if the EPA
determines that an area did not attain the NAAQS by the applicable deadline, the responsible air agency has up to 12
months from the effective date of the determination to submit a revised SIP
for the area demonstrating attainment and containing any additional measures that the EPA may reasonably prescribe that can be feasibly implemented in the area in light of technological achievability, costs, and any non-air quality and other air quality-related health and environmental impacts as required. According to CAA section 179d3, this revised SIP is to achieve attainment of the one-hour SO2 NAAQS
as expeditiously as practicable, but no later than 5 years from the effective date of the areas failure to attain i.e., 5 years after the EPA publishes a final action in the Federal Register determining that the nonattainment area failed to attain the SO2 NAAQS. In addition to triggering requirements for a new SIP
submittal, a final determination that a nonattainment area failed to attain the NAAQS by the attainment date would trigger the implementation of contingency measures adopted under 172c9.
III. Proposed Action Under CAA section 179d2, the EPA
proposes to determine that the St.
Bernard Parish SO2 nonattainment area has failed to attain the 2010 one-hour SO2 standard of 75 ppb by the applicable attainment date of October 4, 2018. This determination is based upon review of 1 the states air quality modeling demonstration, which showed the emission limits and stack parameters required at Rain, the primary source of SO2 emission in the area, that were necessary to provide for the areas attainment and 2 Rains available compliance records. The states dispersion modeling, which was based on the allowable limits in the AOC, showed that with compliance with the limits, modeled design values were close to the SO2 NAAQS. Rain has demonstrated a pattern of difficulty meeting its federally enforceable applicable SO2 emission limits and stack parameters memorialized in its Title V permit and the AOC. Emissions have exceeded those limits, and stack temperatures and flowrates have not met the necessary parameters to demonstrate attainment in the St.
Bernard area, including the deviations noted above during the period between the effective date of the limits and the attainment date and reported underestimation of emissions from the
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